This invention relates generally to rack structures and more particularly to a cantilever rack construction having horizontal arms adapted to frictionally engage with a strong binding action a vertical column in order to support heavy weights and yet be infinitely adjustable as to height.
There is a need in industry for storage facilities capable of storing long heavy objects above the floor. Since the quantity and size of objects to be stored varies from time to time, the spatial dimensions of the rack should be variable so as to permit the storage of larger or smaller amounts of material. Also, the arms must be capable of resisting slippage or deformation. Furthermore, when several varieties of related materials are to be stored, the storage racks must be capable of being adjusted easily to add or delete supporting arms to the rack in order to accommodate separately additional varieties of material.
Numerous specialty racks are known, as is exemplified by the rack structure shown in U.S. Pat. No. 3,854,686. However, these specialty racks use non-standard fabricated parts and are expensive to manufacture. Also, conventional racks may be somewhat deficient in their ability to support a great weight of material and are frequently difficult to set up, and to demount or ship. Further, many conventional racks are not capable of duplex usage, ie., the arrangement whereby cantilever arms extend toward the front and toward the back of the rack. Moreover, other conventional cantilever racks are only adjustable to discrete elevations and are not infinitely adjustable.
It has been found that a vertical column in the nature of an I-beam attached to a suitable base can be provided with a readily adjustable horizontal cantilever arm that has great strength, such rack being capable of having additional cantilever arms applied from time to time as required. The cantilever arms are readily adjustable and are provided with generally vertical, opposing channels which, with a binding action, frictionally engage the flanges of the I-beam type of vertical column so as to provide a support arm of great strength. This type of cantilever rack is shown in U.S. Pat. Nos. 3,335,992 and 3,489,291 which have the features of being readily adjustable to various heights while at the same time permitting the application of a plurality of superimposed arms without the necessity of removing the arms or slipping them over the top.
Other known types of cantilever arms are those shown in U.S. Pat. Nos. 3,251,478 and 4,065,089.
By the early 1970's steel manufacturers converted from tapered-flange sections to parallel-flange Universal, or Wide Flange, beam sections. The parallel-flange beam section is being adopted by the art since it is a more economical section for most purposes. However, the parallel flange itself is weaker than the tapered flange which creates problems in the use of the cantilever racks of the indicated type because of the increasing possibility of failure of the column flanges. While this problem is partially overcome by the design shown in U.S. Pat. No. 4,065,089 because the point of load is at the root of the fillet of the flange as compared with the tip of the flange, there are other problems created with the loading at the root fillet such as penetration failures in light flange columns from the point loading of this construction. Also, this construction is undesirable in that it is necessary to mount all the cantilever arms on the column from the top down.
A limitation of the prior art cantilever rack constructions is their capability of carrying very heavy loads. Under these heavy load conditions the prior art devices are subject to the possibility of column flange tip failure and failure of the connector between the horizontal arm and the column flange.